A Pseudo Wire (PW) is a mechanism that carries a key element of an emulated service from a Provider Edge (PE) to another one or multiple PEs through a Packet Switch Network (PSN). A variety of services are emulated through a tunnel on the PSN. The tunnel includes an Internet Protocol (IP) tunnel, a Layer 2 Tunneling Protocol (L2TP) tunnel, and a Multi-Protocol Label Switching (MPLS) tunnel. The services include an Asynchronous Transfer Mode (ATM), Time Division Multiplexing (TDM), and an Ethernet. The PSN may transmit data payloads of diversified services. An internal data service carried by the PW is invisible to a bearer network. In other words, the bearer network is transparent to a Customer Edge (CE) data stream. A local data unit (such as a bit, a cell, and a packet) arriving through an Attachment Circuit (AC) is first encapsulated into a Pseudo Wires Protocol Data Unit (PW-PDU), and then transferred through a PSN tunnel in a lower-layer bearer network. The PE executes encapsulation and decapsulation processes necessary to the PW-PDU, and any other functions (such as sorting and timing functions) required by a PW service. Currently, three optional PW outer-layer tunnel encapsulation modes exist, which are an IP/User Datagram Protocol (UDP) mode, an L2TP version 3 (L2TPv3) mode, and an MPLS mode respectively. Referring to FIG. 8, FIG. 8 is a schematic reference diagram of a network of a point-to-point PW, in which two PE devices PE 1 and PE 2 provide one or multiple PWs for CE devices CE 1 and CE 2 that are connected to the PE 1 and the PE 2, so that the corresponding CE devices may communicate with each other on the PSN.
An existing mobile bearer network based on a Passive Optical Network (PON) uses the PON to perform mobile bearing on various services from a Base Station (BS). Then, the PON is connected to a network element of a mobile network, such as a Base Station Controller (BSC) of a Second Generation (2G) mobile network, a Radio Network Controller (RNC) of a Third Generation (3G) mobile network, or an access gateway (AGW) of a Long Time Evolution (LTE) mobile network, through a metropolitan area convergence network (such as a PSN).
An operator hopes that an MPLS-based Pseudo Wire Emulation Edge-to-Edge (PWE3) network is completely adopted end-to-end from a PON access segment to the metropolitan area convergence network, so as to provide an end-to-end guarantee for Quality of Service (QoS) of TDM/ATM bearing.
An Optical Network Unit (ONU) and an Optical Line Terminal (OLT) are mass access devices, and are usually Layer 2 devices. However, in order to support the PWE3 at the PON access segment, all ONUs and OLTs are required to upgrade a control plane to Layer 3, and support a routing protocol, for example, a Routing Information Protocol (RIP), an MPLS Label Distribution Protocol (LDP), for example, LDP and a Resource Reservation Protocol (RSVP), and PW LDP, for example, a targeted LDP (T-LDP) or a Border Gateway Protocol (BGP), which causes high complexity and poor scalability to the ONUs and the OLTs. Therefore, a technology that supports the PWE3 on a data plane of the PON access segment under the conditions that the device complexity of an ONU is not increased and a configuration of the ONU needs only to be slightly changed is required.